Self locking pliers



June 17, 1958 D. w. HEALD 2,838,972

SELF LOCKING PLIERS Filed Dec. 25. 1955 DA/N W HEALD United States Patent 2,838,972 SELF LOCKING PLIERS Dain W. Heald, Temple City, Calif. Application December 23, 1955, Serial No. 555,099

6 Claims. c1. 31-339 This invention relates to pliers and particularly to a self-locking pliers. 1

An object of this invention is to provide a convenient hand tool which is particularly adapted to be used as pliers which, when tightened on an object, remains locked and tightened on the object, even though no further force is exerted on the handle, which cannot be unlocked vby spreading force exerted on the jaws, and whichcan easily be opened by pulling the handles apart.

.This invention is carried out by providing a pair of jointed jaws, said jaws being pivoted together, each jaw having a lever attached thereto on the same operative side ofthe pivot so that the levers and jaws are not crossed. Then, spreading the levers pushes the jaws together. A pair of handles are pivoted to each other at a fulcrum, with the fulcrum disposed between the two said handles so that squeezing adjacent ends of the handles together moves the ends apart which are on the other 'side of the fulcrum. An end of each handle is pinned to one of the levers of the pliers. I

One of said handles is provided with a cam surface on the same side of the fulcrum as the jaws, and the other handle is provided with a channel which accommodates a slidable wedge and a pin adapted to be forced against the wedge by the cam.

A feature of the invention resides in an interconnection between the handle having the cam, and the wedge, whereby opening of the handles pulls the wedge from beneath the pin.

Y A related feature of this invention resides in providing the handle with the cam in two segments, the segment to which the aforesaid interconnection is attached being flexible relative to the other segment of the handle,

' whereby the wedge may be moved substantially independently of the cam.

' The above and other features of this invention will be fully understood from the following detailed description and the accompanying'drawings of which:

i Fig. 1 is a plan view, partly in cross-section, of a selflocking pliers according to the invention, showing the pliers in an open, 'or released, condition;

Fig. 2 is a plan view, partly in cross-section, of the pliers in the closed, or gripping condition;

Fig. 3 is a cross-section taken at line 33 of Fig. 2; and

Fig. 4 is a fragmentary view, partly in cross-section, of an optional form of the invention.

In Fig. 1, a pair of self-locking pliers 10 is shown in anopen, or released, position. Jaw means 11, comprises a first jaw 12 having a lever 13, and second jaw 14 having a lever 15. The jaws are joined by a pivot 16 which may s'implybe a pin. A land 17 on each jaw is joined by the pivot, so that the pivot is between the jaws and levers, with the individual jaw-lever combinations uncrossed. Therefore, the jaws will be opened by pressing the levers together, and will be closed by pulling the levers apart. 2

A first handle 18 has a U-shaped cross-section (see *2 Fig. 3) so as to provide a channel 19 between the legs 20 of the cross-section. channel, spaced from the bight 22 of the cross-section.

A locking wedge 23 is slidable in the channel 19 between the bight, legs and block. This wedge has a locking surface 23a which makes an angle 0 with its base 24. The base 24 slides on the bight of the channel.

A locking pin 25 extends into the channel adjacent the end of the block nearest the jaws, and has a locking surface 26 which makes an angle with the base 24 of the wedge which is, preferably equal to 0. The locking pin can thus be shoved against the locking wedge so that the locking surfaces contact each other.

A second handle 27 comprises two segments: a for-.

ward segment 28, and a rear segment 29. The forward segment is U-shaped in cross-section, and folds around a fulcrum block 30. Fulcrum block 30 has an eat 31 with a hole therein which matches holes in the legs 20 of the first handle. A fulcrum is formed between the two handles by placing a fulcrum pin 32 through these holes. Thus, the fulcrum is between both of the handles, and intermediate the ends of both of them, so that squeezing a pair of adjacent ends moves the other ends apart. Rivets 33 hold the fulcrum block in the forward segment of the second handle.

The fulcrum block has an extension 34 which projects beyond the rear end of the forward segment, which ex-- tension has a round hole 35 and an elongated hole 36.

Hole 36 is preferably, although not necessarily, farther The rear segment 29 of the second handle is attached to the extension 34 of, the fulcrum block by pins 38 and 39 in holes 35 and 36, respectively. The rear segment springing; means, which may be such as a coil spring 40, are attherefore can pivot slightly around pin 38.

tached to extension 34 and to the rear segment so as to normally draw the rear segment inward toward the first handle.

Pins 41 and 42 respectively join the first handle to lever 13, and the forward segment of the second handle to lever 15.

A link 43 is pivotally joined to the locking wedge, and to a block 44 attached to the rear segment of the second,

handle, by pins 45 and 46, respectively. The preferred arrangement of pivot 16, fulcrum, and pin 46 is shown in Fig. 2, where with the jaws tightly clamped together, these three elements are in line. While these elements are aligned in the embodiment of Fig. 2, it will be undersingle line, but the pliers will work nearly as well. Slot 49 permits some free play at pin 48.

It is evident that link 43 may have different configurations, and make various angles with the handles of the pliers. The handles themselves may have various, configurations. locking pin 25 and wedge 23 may be varied to suit the Furthermore, the length and angles of Patented June 17, 1958' A block 21 is placed in the requirements of a given plier structure. The pins 45, 46,v 32. and 16 mayalso be repositioned. to suit the re quirements of a given plier design.

The jaw design shown is suitable for many uses, but isqinton'ded tob'e merelyex'emplary of a pair of plier jaws. Various well kn'ownja'ws may be substituted for these,- 'such as cutters, wire twisters, sockets-for welding rods, and water pumps. These are all well-known jaws which require no illustration or further discussion here. ln addition, "rneans may be provided for maintaining parallel jaw" action-in accordance with well-known jaw construction.

The operation of these pliers will now be described. Starting with the pliers in the open position shown in Fig. 1 the handles are squeezed together. This spreads pins '41 and='4 2" apart, and moves jaws 12 and 14 together to clamp on some object such' as a nut, for example.

-During this closingmovement, the rear segment 29 of'the second handle will be in line with the first segment, and will force link 43 to move the locking Wedge toward the jaws. Since the cam 37 is on the opposite side of the fulcrum from the squeezing action, the cam is moved away from channel 19, and this permits locking pin 25 to move away from the advancing locking surface 23a of the locking wedge. The various dimensions of the cam, the link, and the angle will be chosen so that the advance of locking surface 23a is not so rapid that the cam does not permit the locking pin to back off; Otherwise, the device might tend to lock before the jaws are tightened on the object.

However, the provision of the second handle in two segments does result in a significant dimensional flexibility, for as the handles are squeezed together, there is a force against the cam which tends to move the ex tension 34 toward the first handle. Were the second handle in a single piece, this would, of course, tend to jam the locking wedge even more tightly against the locking pin, and the relative dimensions of the device would be fairly critical. However, with the. slight pivoting-allowed the rear segment 29, the said movement of the extension 34 can be accomplished independently 'then the jaws can continue to close.

Wlien the jaws firmly grip the object, then there can be no further movement of the cam, and the link 43 shoves the wedge firmly under the locking pin, with pin 39 solidly against the inner wall of elongated hole 36. The pliers are now locked on the object. Such a condition is shown in Fig. 2, where the jaws are simply closed on one another.

Now if an effort be made to. pry the jaws apart, or press the handles together on the jaw side of the fulcrum, the cam will simply press down on the locking pin, which thereupon presses on the wedge. Any suitable angle 6 may be used, but in practice a gentle slope is preferred, angle 0 preferably being in the range from 25 to 35, 35 being the presently preferred value, and the effect is simply to lock the locking wedge in place, rather than slide it, and the jaws are thus held closed. However, angles 6 less and greater than 25 35 respectively, are within the scope of this invention. The play in the second handle prevents any slight movement of the handles from withdrawing the locking wedge by pulling on link 43.

When the pliers are to be opened, the condition shownin Fig. 1 results. Pulling the rear ends of the handles apart withdraws the wedge by means of line 43, and this permits the cam to press the locking pin toward the. lockingwedge. However, the wedge is pulled from beneath the locking pin at least as fast as the pin approaches surface 23a, so that the pliers can be opened.

1 The provision of the second handle in two segments eases the opening action, and also makes the relative dimensions. less. critical,.inasmuch. as, if the cam presses the locking pin so firmly against the locking wedge that the wedge tends to be impeded from being withdrawn, the rear segment can pivot around pin 35 and move the wedge out from beneath the locking pin with out moving the cam. Then, when the wedge is slightly moved, the cam can again move, and the jaws will be released.

The slots 47 and 49 allow some further flexibility of the link and wedge action.

Tests have been made to determine the operability of this device and it has been found that, utilizing 6- inch handles, and a 1 inch jaw, a light hand squeeze on the handles results in a grip on an object which has not been dislodged, even by placing the front ends of the handles in a vise and applying an extremely great force thereto. In fact it has been found that the tool will be destroyed before the jaws can be pried apart.

This invention is not to be limited by the embodiments shown in the drawing and described in the description, which are given by way of illustration and not by way oflimitation, but only in accordance with thescope of the appended claims.

I claim 1. A self-locking pliers, comprising: two jaws, two

levers, each of said levers being integral with a difierent' one of said jaws; a pivot joining said jaws, each jaw and its integral lever being on a single side of the pivot,

whereby spreading thelevers moves the jaws together; a first handle having a channel therein; a second handle;

said handles being pivotally joined by a fulcrum, said adjacent ends of the handles being attached to the levers,

each lever being attached to a different one of said handles, whereby pressing the handles together on the end of'the handles remote from the jaws moves the jaws together; a wedge slidably fitted in said channel; a sloping locking surface on said wedge; a locking pin slidably disposed in said channel; a locking surface on said locking pin adapted to engage said locking surface on the wedge; a cam on said second handle engaging, the

locking pin to force it toward the wedge, said locking. pin and cam being on the side of the fulcrum nearest the jaws; and a link attached to and interconnecting the wedge and the second handle on the opposite side of the fulcrum from the jaws; whereby pressing together the endsv of the handles remote from the jaws closes the jaws, and forces the locking. wedge under the locking. pin to prevent the jaws from opening, and whereby pulling apart said-handle ends pulls said locking wedge from beneath said locking pin to permit the jaws to open.

2. Apparatus according to claim 1 in which the locking, surface of the wedge makes an angle of between 25 and 35 with the base of. the wedge.

3. Apparatus according to claim 1 in which the lockingsurface of the wedge makes an angle of approximately 35 with the base of the wedge.

4. A self-locking pliers, comprising: two jaws, two

levers, each of said levers being integral with a different one of said jaws; a pivot joining said jaws, each jaw and its integral lever being on a single side of the pivot, whereby spreading the levers moves the jaws together; a first handle having a channel therein; a second handle;v said handles being pivotally joined by a fulcrum, said handles being. on opposite sides of the fulcrum whereby spreading one pair of adjacent ends of said handles moves. the other pair of adjacent ends together, one pair of adjacent ends of the handles being attached to thelevers, each lever being attached to a different one of said handles, whereby pressing the handles together on the end of the handles remote from the jaws moves the jaws together; a wedge slidably fitted in said channel; a sloping locking surface on said wedge; a locking pin slidably disposed in said channel; a locking surface on said locking pin adapted to engage said locking surface on the wedge; a cam on said second handle engaging the locking pin to force it toward the wedge, said locking pin and cam being on the side of the fulcrum nearest the jaws; and a link attached to and interconnecting the wedge and the second handle on the opposite side of the fulcrum from the jaws; whereby pressing together the ends of the handles remote from the jaws closes the jaws, and forces the locking wedge under the locking pin to prevent the jaws from opening and whereby pulling apart said handle ends pulls said locking wedge from beneath said locking pin to permit the jaws to open; said second handle comprising two parts: a forward segment adjacent the jaws, and a rear segment, said rear segment being pivotally mounted to said forward segment, said link being rigid and attached to the said rear segment whereby the wedge can be moved by the rear segment 6 without moving the forward segment of said second handle.

5. Apparatus according tr: claim 4 in which said link has a slot therein, and is joined by pins to the wedge and to the rear segment, one of said pins projecting into said slot so as to be slidable therein and permit free move ment of said second handle independently, of movement of the wedge.

6. Apparatus according to claim 4 in which the rear segment is mounted to the forward segment by means of a pair of pins, one of said pins being laterally shiftable in one of said segments.

References Cited in the file of this patent UNITED STATES PATENTS 

